RELEVANCE: Fertilization is biological process with important medical, social and economic implications. From extensive study, the events of fertilization are known in some detail. However, the molecular underpinnings of these events generally remain elusive. Most previous work on fertilization has relied on biochemical and immunological approaches. Our work is groundbreaking in the application of classic gentic analsysis to this vital area of research. RATIONALE: Many of the genetic and molecular tools developed for C. elegans are not available or are very difficult to utilize in other organisms traditionally used for studying fertilization. One of the most significant advantages of C. elegans is the ability to isolate and maintain mutants that affect sperm or eggs and no other cells. Previously, through the study of sterile mutants, we have identified some of the first molecules required for productive gamete interactions in C. elegans. We aim to get a better understanding how sperm molecules (SPE-9, SPE-38, SPE-41/TRP-3 and SPE- 45/Izumo) and oocyte molecules (EGG-1/2) functions to insure successful fertilization. The SPE-45/Izumo gene represents a conserved sperm function from worms to humans. Futher, a full understanding of the molecular mechanisms of fertilization is impossible without a more complete inventory of molecular components. Therefore we aim to identify new fertilization molecules through genetic and molecular analysis. Particular emphasis will be placed on the identification of genes required in oocytes. OBJECTIVES: The goal of this proposal is to further our understanding of fertilization in C. elegans by conducting the following experimental aims: 1) Determine the molecular nature of new gamete function genes defined by a fertilization defective mutant phenotype. 2) Investigate mechanistic connections, functions and fertilization pathways of previously identified gamete function molecules. 3) Conduct a saturation mutagenesis for fertilization mutants taking advantage of an innovative genetic screening strategy that enriches for gamete function mutants. This work will complement fertility studies in other organisms as well as provide insights into the mechanisms of cell-cell interactions and the diversity of reproductive strategies.